TEHRAN, Iran—When Laila Esmaeili and her brother, Hasan, get together every week at their father’s apartment in southern Tehran, the political discussions can get heated.

Ms. Esmaeili said she supports moderate incumbent President
Hassan Rouhani
in Iran’s presidential election on Friday. The 35-year-old mother said she chafes at the head scarf Iran requires women to wear in public.

Hasan Esmaeili said he backs Mr. Rouhani’s main opponent, hard-liner Ebrahim Raisi. “Sometimes we argue,” said Mr. Esmaeili, 33, who is studying architecture. “She doesn’t defend Rouhani much because she doesn’t have good information.”

Iran’s struggling economy could be decisive. Ordinary Iranians have seen few benefits from the end of sanctions that accompanied the nuclear deal, and Mr. Rouhani’s approval ratings have fallen steadily since it took effect at the start of 2016.

Hasan Esmaeili stands next to a large picture of his brother, who died in the Iran-Iraq war, and other pictures.
Photo:
Mojgan Ghanbari for The Wall Street Journal

On the other hand, inflation has fallen on Mr. Rouhani’s watch from a peak of above 40% to a more manageable 12% in March. Official figures put the unemployment rate at almost 13%, and 42% of respondents in an April survey by IranPoll.com said it was the top issue in the election.

Mujtaba Alvandi, 56, lives in a working-class neighborhood of Tehran. He said Mr. Rouhani hasn’t done enough to help the poor and said he plans to vote for Mr. Raisi.

He said his daughters plan to vote for Mr. Rouhani, and added that one of them, a college student named Fatima, has been especially vocal in arguing that Mr. Rouhani should be given a chance to fully execute his agenda.

How will Iran react to worsening tension with the U.S.? That will, in part, be determined when Iranians head to the polls on May 19, in a contest between moderate President Hassan Rouhani and a slew of conservative candidates. WSJ's Niki Blasina reports. Photo: Getty Images.

“She says if you want to start running a business or a company, it takes a long time,” he said. “It’s the same for a country.”

The divide is generational in some cases. While many parents grew up around the time of the 1979 Iranian revolution, younger voters often don’t remember those events or the hostage crisis that triggered decades of hostility with the U.S.

In her conservative Tehran family, Atie Ranjbar says she is the only one who supports Mr. Rouhani. The 22-year-old law student said she is trying to persuade her brother and sister.

“In the case of young people’s issues, I told them if Raisi comes, things are going to get worse,” she said.

At recent rallies, Mr. Rouhani has said the election presents Iranians with a choice between moving forward or back to the era of his predecessor, hard-liner Mahmoud Ahmadinejad, who oversaw rocketing inflation and stagnating economic growth later in his second term.

A Rouhani supporter held a poster during a campaign rally in Tehran on Tuesday.
Photo:
Ebrahim Noroozi/Associated Press

Mr. Raisi enjoys broad appeal among religious conservatives and supporters of Iran’s Supreme Leader Ayatollah
Ali Khamenei,
who has final say in most matters of state. Mr. Raisi served for decades in Iran’s opaque judiciary.

Mr. Raisi wasn’t seen as a formidable challenger until recently, and his rapid rise could indicate that the 77-year-old Mr. Khamenei considers him as a potential successor, according to analysts who follow Iran. Mr. Khamenei last year appointed Mr. Raisi custodian of a multibillion-dollar charity at the heart of an economic empire Mr. Khamenei oversees.

For Mohammad, a 60-year-old taxi driver in Tehran who declined to give his last name, Mr. Raisi’s invocations of religion’s role in politics—and his appeal to religious voters—has been divisive. He said his entire family supports Mr. Rouhani, except his son, a Shiite Muslim cleric.

“We argue at home,” he said. “My son talks about the honesty of Mr. Raisi, but I say I haven’t seen the practicality of him or him putting words into action. I say to him that even if Rouhani hasn’t done so much, at least we have stability and society is completely different from Ahmadinejad’s time.”